A recent innovation in materials science is the development of “smart surfaces” that have reversible properties. In particular, scientists are developing an approach for “dynamically controlling interfacial properties that uses conformational transitions (switching) of surface-confined molecules.” (A Reversible Switching Surface—Science Magazine, 18 Oct. 2002). As explained further in MIT News (MIT's Smart surface Reverses Properties—Jan. 16, 2003), researchers describe “an example of their new approach in which they engineered a surface that can change from water-attracting to water-repelling with the application of a weak electric field. Switch the electrical potential of that field from positive to negative and the surface reverts to its initial affinity for water.” The smart surface has a plurality of surface-confined molecules, sufficiently spaced to undergo conformational transitions in response to an applied voltage to preferentially expose hydrophilic or hydrophobic portions of the surface-confined molecules. This is shown diagrammatically in the above articles as a downward, lateral bending of the molecules in response to the applied voltage. The molecules have hydrophilic or “water-loving” tops, exposed in the absence of the applied voltage. When bent down, the molecules expose hydrophobic or “water-repelling” loops. A suggested application of this emerging technology is the manipulation of molecules in fluids, such as the “bioseparation” of one molecule from another.
The oil and gas industry has long been interested in improving ways to “manipulate molecules” and separate fluids. In the production of hydrocarbons from formations, superfluous components such as water are often produced. The oil must be separated from the water and other components before it can be used. Conventional separators typically rely on the difference in densities between oil and water, separating the fluids via gravity or centrifugal force. Centrifugal separators separate the oil and water mixture in a rotating vessel such that the oil segregates inwardly while the water segregates outwardly. Hydrocyclonic separators rotate and separate the fluid mixture without the use of a rotating vessel. Gravity separators separate oil in a static vessel, allowing the lighter oil to segregate upwardly and the higher density water to segregate downwardly. Examples of various separators are discussed in U.S. Pat. Nos. 6,550,535, 6,436,298, 5,916,082, 5,565,078, 5,195,939, and 5,149,432.
Downhole separation in oil wells is increasingly attractive because the separated water can be readily re-injected into a downhole water bearing formation without removing it from the well bore. This obviates the need for surface tanks, separators, and water disposal systems, reducing costs and the possibility of environmental damage. Environmental concerns may simultaneously complicate this approach, however, requiring a relatively high degree of purity of the re-injected water. Using existing separation techniques, the high degree of separation required by regulations and environmentally responsible production of hydrocarbons is generally not attainable. In addition, if significant oil is injected into the disposal zone with the water, the water bearing formation may be adversely affected by the oil, causing blockage and/or reduced permeability of the injection interval.
Another problem with existing separation devices and methods is the amount of energy consumed in the process, and related costs. Although the industry typically generates high revenues from the production of oil and gas, the associated costs are typically on the same order of magnitude. The industry therefore constantly strives to improve efficiency in all areas of production. As a result, efficiency in separation is as important as efficiency in other areas of production.
There is a need for an improved approach to separating oil, water, and other fluids and solids. Whatever can be done to increase the efficiency of existing separation techniques will ultimately benefit not only the oil and gas industry, but society as a whole.